Magnetocaloric refrigeration is a process in which the entropy of a magnetocaloric material is modulated by a magnetic field, such that the material acts as a refrigerant, pumping heat from a lower-temperature source to a higher-temperature sink. Magnetocaloric refrigeration processes typically fall into either a near-room-temperature category or a cryogenic category, with the intended application resulting in different magnetocaloric materials and/or system configurations being used.
In some applications requiring cryogenic refrigeration, traditional methods of cryogenic refrigeration are unsuitable. For example, certain medical (e.g., MRI) and other small-scale applications employ liquefied helium or other cryogens, which have very low boiling points, for example, 4K for helium. Industrial compressors and other equipment designed to liquefy helium in conventional mechanical cycles may be efficient to liquefy large quantities of cryogens, but inefficient at smaller volume design points. Further, such industrial machinery may be prohibitively expensive for these applications. However, suitable magnetocaloric materials for such cryogenic applications may not be readily available. Accordingly, such cryogenic consumers typically purchase helium liquefied by a third party, use it, and then allow the gaseous helium to re-enter the environment. However, such methods require continual helium purchase, while the accessible supply thereof may be limited and prices subject to fluctuation.
What is needed, then, are systems and methods to economically liquefy and/or re-liquefy a cryogen such as helium.